The proposed research is designed to determine some of the relationships between brain damage, behavioral recovery and aging. It is only within the last few years that increasing attention has been focused upon the question of neural plasticity in the adult CNS and almost nothing is known about the behavioral concomitants of plasticity (or even whether it exists) in the senescent organism. Three primary experimental projects have been proposed. The first deals with the question of long-term, or longitudinal, changes in cognitive performance in the rat after it has received one or two-stage frontal ablations as a young adult. This project is designed to determine whether the "sparing of function" observed after serial, frontal lesions in young adults, is maintained throughout the animal's normal life span, and what, if any, changes take place in performance as the animals approach old age. The second project is an attempt to determine whether general environmental enrichment or specific programs of training before or after brain damage can ameliorate the effects of CNS lesions in aged rats. The third project deals with specific attempts to facilitate recovery of function by drug treatment prior to, or immediately after, brain damage. An attempt is made to determine whether the hypothesis of "denervation supersensitivity" can serve as a model for recovery after brain damage. The alternative, or secondary, experiment, tests the hypothesis that brain damage blocks "access to engrams" which may be retrieved by appropriate drug treatments.